The present invention relates to antitussive application of octahydroisoquinoline derivatives.
Codeine known as a representative antitussive capable of securely stopping cough acts on opioid xcexc receptors to basically cause adverse effects such as drug dependence, respiratory depression, constipation, central inhibition, etc. Therefore, there is demand for a strong antitussive which can be used with safe, and from which the opioid xcexc acting adverse effects possessed by codeine are removed.
Although Japanese Unexamined Patent Publication No. 4-275288 discloses compounds of the present invention as opioid xcex4 agonist having a new skeleton, known technologies, including the patent of this publication, do not suggest that the compounds of the present invention having the new skeleton have an antitussive action.
An object of the present invention is to provide a strong antitussive without grave adverse actions such as drug dependence, respiratory depression, constipation, central inhibition, etc.
The present invention provides an antitussive comprising, as an active component, one of octahydroisoquinoline derivatives represented by the following formula (I) or pharmacologically acceptable acid addition salts thereof, and a therapeutic method using the same. 
wherein R1 represents alkyl having 1 to 5 carbon atoms, cycloalkylalkyl having 4 to 7 carbon atoms, cycloalkenylalkyl having 5 to 7 carbon atoms, aralkyl having 7 to 13 carbon atoms, alkenyl having 3 to 7 carbon atoms, furan-2-yl-alkyl (wherein an alkyl moiety has 1 to 5 carbon atoms), or thiophene-2-yl-alkyl (wherein an alkyl moiety has 1 to 5 carbon atoms); R2 represents hydrogen, hydroxy, alkoxy having 1 to 5 carbon atoms, or alkanoyloxy having 1 to 5 carbon atoms; R3 represents hydrogen, hydroxy, alkoxy having 1 to 5 carbon atoms, alkanoyloxy having 1 to 5 carbon atoms, or aralkyloxy having 7 to 13 carbon atoms; X represents CH or N; m represents an integer of 0 to 2; m R4 groups independently represent fluorine, chlorine, bromine, iodine, alkyl having 1 to 5 carbon atoms, alkoxy having 1 to 5 carbon atoms, nitro, amino or alkylamino.